Fold able fin



March 24, 1964 s. KONGELBECK 3,125,956

FOLDABLE FIN Filed Oct. 10, 1961 s Sheets-Sheet 1 SVERRE KONGELBEQKINVENTOR ATTORNEYS March 1954 s. KONGELBECK FOLDABLE FIN 3 Sheets-Sheei2 Filed Oct. 10, 1961 /,//////A il! Ii .7

SVERRE KONGELBECK INVENTOR ATTORNEYS March 1954 s. KONGELBECK FOLDABLEFIN 3 Sheets-Sheet 5 Filed 001;. 10. 1961 FIG. 6.

SVERRE KONGELBEOK INV EN TOR ATTORNEYS United States Patent 3,125,956FOLDABLE FEN Sverre Kongelbeek, Silver Spring, Md, assignor to theUnited States of America as represented by the Secretar y of the NavyFiled (Bet. 10, 1961, Ser. No. 144,272 4 Claims. (Cl. 1025tl) Thisinvention relates generally to fins for aerial missiles, and moreparticularly to an improved, economical to construct, foldable fin foruse on service and simulated rocket missiles.

It has become common where it is necessary to conserve storage andhandling space to furnish certain missiles with foldable fins, the finsbeing folded during storage and until just before launching. Severalconstruc-. tions for folding fins have been proposed, among which isthat shown in US. Patent No. 2,925,966, granted to the instant inventor.However, a need has existed for a structurally uncomplicated andeconomical foldable fin for use on missiles generally, and in particularon simulated, or dummy, missiles utilized for training purposes. Thefins utilized on simulated missiles, in addition to being economical,should be designed so as to insure that they will remain folded untilerection is desired, and that when erect they will be structurallystable.

It is, therefore, the principal object of this invention to provide afoldable fin so constructed as to be self-retained in folded positionuntil erection is desired, and to be structurally stable after erection.

A further object of the invention is to provide a foldable fin that ismechanically uncomplicated and economical of construction.

Another object of this invention is to provide able fin so constructedas to be easily movable folded to an erect position.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following deailed description when considered inconnection with the accompanying drawings, wherein:

FIG. 1 is a perspective of the aft end of a missile, showing fourfoldable fins in their erect positions;

FIG. 2 is an end elevation of the missile, showing the fins in theirfolded positions;

FIG. 3 is a side elevation of the rear face of one of the fins;

FIG. 4 is a cross-section on line 44 in FIG. 3, showing the constructionof the latch mechanism;

FIG. 5 is an enlarged elevation, partially broken away, of a portion ofthe front face of a fin; and- FIG. 6 is a sectional view similar to FIG.4, showing the fin in a folded position.

The foldable fin of the present invention includes a base portion and abody portion hingedly connected by a pin which passes throughinterleaved projections on the two portions. One of the projections onthe body portion carries a cam surface disposed transverse to the planeof said portion, said cam surface having a pair of circumferentiallyspaced notches therein. The base portion contains a spring biased latchpin positioned to engage the cam surface, said pin cooperating with thetwo notches in the cam surface to retain the pin in either an erect or afolded position. The shape of the notch which coopcrates with the latchpin to retain the fin in a folded position is such that if a sufficienterecting force is exerted the pin will be disengaged, thus permittingerection of the fin. During the erecting, or unfolding, movement thelatch pin rides upon the cam surface until the fin is fully erected, atwhich point it enters the second notch to secure the fin in position.

Referring now to the drawing, the aft end of a missile a foldfrom a isindicated at 2, and has four foldable fins 4, 6, 8 and 10 attachedthereto. As is best shown in FIG. 2, the fins 4 and S are constructed tofold in a clockwise direction, whereas the fins 6 and 10 fold in acounter-clockwise direction, the fins being folded with adjacent onesoverlapping.

The four fins, save for the direction in which they fold, areconstructed in an identical manner, and hence only the fin 4 will bedescribed. The fin 4 includes a root or base portion 12 and a bodyportion 14, the base portion having laterally projecting flanges 16 and18 and being secured to the missile 2 by suitable fasteners 20 whichextend through openings in said flanges and engage with threaded boreswithin a boss 22 on the missile. The base 12 extends longitudinally ofthe missile, and has a pair of upstanding projections 24 and 26 thereonwhich have aligned, longitudinally extending bores 28 and 3t)therethrough, respectively. Each bore is fitted with a suitable bushing32 or 34 (FIG 5).

The base portion has a bore 36 extending normally therethrough andopening midway between the two projections 24 and 26, the upper end 33of said bore being enlarged to define a radial shoulder 40. A pair ofaligned, vertically elongated openings 42 and 44 extend transverselythrough the base portion and open into the vertical bore 36, saidopenings being positioned medially of the height of said base. The boss22 on the missile has an opening 46 therein positioned to confront thevertical bore 36 (FIGS. 4 and 6). Disposed within the bore 36 andextending through opening 46 is a cylindrical sleeve 43, said sleevebeing of a size to fit tightly within said bore and having an out-turnedlip 50 which is received within the enlarged bore portion 38 and whichrests upon shoulder 46 Disposed within sleeve 48 is a latch pin 52, saidpin having a rounded, chisel-shaped upper end 54 and a transverse slot56 extending therethrough below said upper end (FIG. 4). The sleeve 48has a pair of confronting, elongated vertical guide slots 58 and 69therein, and a guide pin 62 is received within a transverse bore in thepin 52 below the slot 56 and extends through said slots 53 and 6% Theguide pin functions to limit the extent to which the latch pin may slidewithin its housing, and to prohibit relative rotation therebetween.Positioned between the lower end of the latch pin and the lower end ofthe sleeve is a coil spring 62, which is retained in position by awasher 64 and an inturned lip 66 on the sleeve. The transverse slot 56in the latch pin and slots 58 and 6%? in the sleeve are positioned toconfront openings 42 and 44, and are so dimensioned that a pointedtool63 (shown by phantom lines in FIG. 4) may be inserted therethrough todepress the latch pin against the force of spring 62.

The body portion 14 of the fin has a pair of projections 70 and 72thereon which, together with the lower, trailing part 74 of the body 14,define a pair of notches 76 and 73 of a size to freely receive theprojections 24 and 26. The projection 70 and the trailing part 74 of thefin body have flat end faces 80 and 32 thereon, which are presented tothe notches 76 and 78. Similarly, the projections 24 and 26 have flatend faces S3 and thereon, the distance measured between said faces 83and 85 being slightly less than the distance between the faces 8% and82. The notch defined between the projections 24 and 26 is ofsubstantially greater width than is the projection 72 which is receivedtherein. The projections 70 and 72 and the trailing edge 74 have,respectively, aligned bores 34, 86 and 88 therein. To assemble the bodyportion 14 of the fin to the base portion 12, the projections 24 and 26and the projections 70 and 72 are interleaved, with the bores 84, 28,86, 30 and 88 aligned. A pin 90 is then inserted through said bores, andis retained in position by a key 92 which passes through alignedopenings in said pin and fin portion 74. The notches 76 and 78 are of aheight sufiicient to permit the fin to easily fold.

The projection 72 has a rounded cam surface 94 thereon, the radius ofwhich (measured from the center of bolt 90) decreases progressively froma maximum at the upper end 96 thereof to a minimum at its lower end 98(FIG. 4). The cam surface has a shallow, rounded groove 100 near itsupper end, and a deep, wedge-shaped groove 102 adjacent its lower end.The rear wall of groove 102 is defined by a rounded boss 104 on the rearface of projection 72, which boss projects radially substantiallyfurther than the bottom 98 of cam surface 94 to define an engagementface 106. The groove 1% is so positioned that it will confront the tip54 of latch pin 52 when the fin body 14 is in its folded position.Similarly, the groove 102 is so positioned that it will confront the tip54 when the body 14 is in its erect position.

In operation, the fin body 14 is initially in its folded position (FIGS.2 and 6), with the rounded tip 54 of latch pin 52 received withinrounded groove 100. The force of spring 62 on the pin 52 is sufiicientto retain the fin in this folded condition until a substantial erect ingforce is exerted thereon, whereupon the rounded surfaces of tip 54 andgroove 100 will cooperate to depress the pin 52, thus releasing the finbody 14 for rotation about bolt 90. While the fin body is rotating toits erect position the tip 54 rides upon cam surface 94. The speed oferection of the fin is normally exceedingly fast (erection beingnormally accomplished by powerful, mechanical mechanisms such as thatshown in US. Patent No. 2,977,880) and it is therefore desirable toovercome the inertia of pin 52 as soon as possible, preferably before itmust move into groove 102. The declining radius of cam surface 94accomplishes this by permitting the pin to move upwardly a small amountduring rotation of the fin body 14. The declining radius also serves amore important purpose, in that it insures that a substantial portion ofthe pin will be presented for engagement with engagement surface 106.

As the fin becomes erect, engagement surface 106 on boss 104 engages thelatch pin 52, thus stopping rotational movement of the former.Immediately upon erection of the fin body, latch pin 52 moves upwardlyinto notch 102, the tapered walls of the latter cooperating with therounded, wedge-shaped tip 54 to tightly lock the fin in its erectposition. To fold the fin the tool 68 is utilized to depress pin 52,after which the body portion 14- may be folded down.

It is to be understood that while only one retaining pin and cam surfaceassembly is shown, in certain instances it may be desirable to employtwo or more such assemblies. This might be necessary for large and bulkyfins because of strength considerations, and accordingly the use of aplurality of such assemblies is considered within the scope of theinvention.

Obviously, many modifications and variations of the present inventionare possible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. A foldable fin for an aerial vehicle, including a base portion havinga plurality of upwardly extending, spaced projections thereon, a bodyportion having a plurality of downwardly extending, spaced projectionsthereon, said projections on said base and said body portions beinginterleaved and having aligned bores extending therethrough, a pindisposed within said bores for hingedly connecting said two portions, agenerally arcuate convex cam surface on at least one of said projectionson said body portion, said cam surface being disposed normally to saidbody portion and said base portion and having a pair of spaced groovestherein, one of said grooves being defined by rounded surfaces and beingdisposed near the top of said cam surface and the other of said grooveshaving a wedge shape and being disposed at the bottom of said camsurface, and a spring-biased detent means for each cam surface, saiddetent means being disposed within said base portion and positioned toengage said cam surface, said detent means being engageable with saidone of said grooves for retaining said body portion in a folded positionagainst relatively small erecting forces, and being engageable with saidother of said grooves for securing said body portion in position afterit has been erected.

2. A foldable fin as recited in claim 1, wherein the radius of said camsurface decreases progressively from said one groove toward said otherof said grooves.

3. A foldable fin as recited in claim 1, wherein said base portion has avertical bore therein for each detent means, and wherein said detentmeans includes a cylindrical sleeve disposed within said vertical bore,a latch pin disposed within said sleeve, a coil spring disposed withinsaid sleeve in a position to urge said latch pin upwardly, and meansattached to said latch pin and cooperable with said sleeve forrestraining the movement of said latch pin.

4. A foldable fin as recited in claim 3, wherein additionally said baseportion has elongated openings therein positioned to confront each saidvertical bore, and wherein said latch pin and said sleeve haveconfronting slots therein positioned to confront said openings, wherebya tool may be inserted into said slot in said latch pin for depressingit against the force of said spring.

References Cited in the file of this patent UNITED STATES PATENTS2,797,658 Doty July 2, 1957 2,858,765 Startzell Nov. 4, 1958 2,925,966Kongelbeck Feb. 23, 1960 3,031,967 Jasse May 1, 1962

1. A FOLDABLE FIN FOR AN AERIAL VEHICLE, INCLUDING A BASE PORTION HAVINGA PLURALITY OF UPWARDLY EXTENDING, SPACED PROJECTIONS THEREON, A BODYPORTION HAVING A PLURALITY OF DOWNWARDLY EXTENDING, SPACED PROJECTIONSTHEREON, SAID PROJECTIONS ON SAID BASE AND SAID BODY PORTIONS BEINGINTERLEAVED AND HAVING ALIGNED BORES EXTENDING THERETHROUGH, A PINDISPOSED WITHIN SAID BORES FOR HINGEDLY CONNECTING SAID TWO PORTIONS, AGENERALLY ARCUATE CONVEX CAM SURFACE ON AT LEAST ONE OF SAID PROJECTIONSON SAID BODY PORTION, SAID CAM SURFACE BEING DISPOSED NORMALLY TO SAIDBODY PORTION AND SAID BASE PORTION AND HAVING A PAIR OF SPACED GROOVESTHEREIN, ONE OF SAID GROOVES BEING DEFINED BY ROUNDED SURFACES AND BEINGDISPOSED NEAR THE TOP OF SAID CAM SURFACE AND THE OTHER OF SAID GROOVESHAVING A WEDGE SHAPE AND BEING DISPOSED AT THE BOTTOM OF SAID CAMSURFACE, AND A SPRING-BIASED DETENT MEANS FOR EACH CAM SURFACE, SAIDDETENT MEANS BEING DISPOSED WITHIN SAID BASE PORTION AND POSITIONED TOENGAGE SAID CAM SURFACE, SAID DETENT MEANS BEING ENGAGEABLE WITH SAIDONE OF SAID GROOVES FOR RETAINING SAID BODY PORTION IN A FOLDED POSITIONAGAINST RELATIVELY SMALL ERECTING FORCES, AND BEING ENGAGEABLE WITH SAIDOTHER OF SAID GROOVES FOR SECURING SAID BODY PORTION IN POSITION AFTERIT HAS BEEN ERECTED.